In the 19th century, the anthropologist Samuel George Morton set out on the, by today's standards, highly dubious quest to show that cranial capacity differs between racial groups. Essentially, he filled almost a 1000 skulls with seed or leadshot, gave each of them a good shake to make sure that every nook and cranny was filled, and then measured the amount of filling that came out as he emptied the skulls. According to his findings, Caucasians had the largest skulls. As, of course, he had suspected all along.

Morton's experiments were not that famous until, more than a century later, they were rediscovered by the eminent biologist Stephen Jay Gould. And he was having none of it. According to Gould, Morton's findings were driven by his racist expectations. Caucasian should have the largest cranial capacity, so, when measuring the skulls, Morton made sure that they did, perhaps merely by subtle “unconscious or dimly perceived finagling.” Gould used this example to prove his broader point that experimental results are inevitably biased, because researchers are only human and simply cannot help but massage the data just the tiniest bit. And, as they say, if you torture the data it will confess to anything.

Now, I'm in general sympathetic to Gould's views, but in this case he was wrong. In a recent study in PLoS Biology, Lewis and colleagues remeasured almost half of the skulls that had been used by Morton (Gould did not have access to the actual skulls. He derived his argument from scrutinizing Morton's writings.). Their findings are perhaps surprising. Morton's measurements were in general accurate and the few mistakes that he made did not “favor” the Caucasians. In my opinion, this actually proves Gould's point. The idea that Caucasians have a larger cranial capacity than other racial groups did not fit into Gould's view of the world. And therefore he couldn't help but discredit the study that showed this to be the case. Unfairly, as it turns out.

Lewis and colleagues are quite apologetic in their paper. I don't think that this is necessary, but they probably fear that their paper will be interpreted as affirming racist beliefs (and thereyou go). But their study is not about that: Even if there are minor differences, does anybody really believe anymore, as both Morton and Gould apparently did, that you can derive conclusions about intelligence from cranial capacity? (Probably yes, but those people will not be too sensitive to scientific arguments anyway.) The more interesting point is that nobody escapes the fallacy of deriving conclusions from expectations, rather than from data. Not even Stephen Jay Gould!

Morton, S. G. (1839). Crania Americana, Or, A Comparative View of the Skulls of Various Aboriginal Nations of North and South America: to which is Prefixed an Essay on the Varieties of the Human Species. London, United Kingdom: Simpkin, Marshall.